Previously known heat pumps of the type to which the invention relates comprise a condenser, restriction means, an evaporator and a compressor. A coolant, such as Freon.RTM., is pumped in a cycle through these components and carries heat energy from the evaporator at a low temperature to the condenser at a higher temperature. The condenser is connected to a heat receiver, such as a warm water accumulator, and the evaporator is connected to a heat emitter, such as the ambient air, well-water, salt water, soil heating loops, solar panels, heating from stables, or waste heat.